In stamping presses which are used for blanking, drawing, punching and piercing relatively small sheet metal objects, it is conventional to fasten the dies within retainer plates or rings which, in turn, are fastened to the press platens and the like movable parts. Such dies, including punching and forming dies, are removable from the retaining rings or plates for replacement when desired.
Examples of such type of presses and retainers within which die parts are fastened are illustrated in U.S. Pat. No. 2,089,795 issued Aug. 10, 1937 to Hodge, U.S. Pat. No. 2,699,830 issued Jan. 18, 1955 to Hodge and U.S. Pat. No. 3,213,729 issued Oct. 26, 1965 to Koch. The press illustrated in the Koch patent is of a horizontally movable type which is particularly useful for accurately stamping small sheet metal parts from larger sheets.
In the conventional presses, the retainer rings or plates, normally comprise a relatively thick metal plate which may be circular or polygonal in shape, having a socket which usually is circular. The die is provided with a part which fits within the socket where it is locked during stamping use. The locking mechanism which is conventionally utilized is in the form of a lock screw.
Conventional lock screws, such as is illustrated in U.S. Pat. No. 2,017,247 issued Oct. 15, 1935 to Hodge, comprise a threaded shank and a circular head which is provided with a notch or elongated cut-away. The threaded shank fits within a threaded opening in the retainer and the head is arranged to overlap the socket and to fit into a groove or channel formed in the die part which fits within the socket. Thus, rotation of the screw results in a portion of the screw head fitting into the groove or channel in the die. For unlocking, the screw is rotated oppositely and its notch is aligned with the edge of the socket and the surface of the die part so that the die part can then be removed because the screw head no longer fits within the groove.
That type of locking screw, namely the notched head locking screw has been used for many years for fastening various die inserts, including punches and the like, within retainer sockets. The same lock screws may be used to secure together various die parts or tooling parts which interfit in the same manner as described above.
In typical uses, the tool or die maker provides threaded holes in the retainer using conventional tapping tools for that purpose. The screws are correspondingly threaded. Then such screws are fastened within the threaded or tapped holes as required.
In the past, such screws presented a number of problems, including a tendency to break or loosen, failure of the screw head to provide adequate or complete engagement with the retainer, and the like.
Consequently, the invention herein relates to an improvement in the notched head type of tooling lock screw and in the method of making and using same.